So you're saying there's no such notation?
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PolynomialMay 25 '12 at 9:44

4

@Polynomial He's saying that in your example such a notation is not necessary, because it's implicit in the parameters of $f$. A function by definition only knows what it sees in its parameters.
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CodesInChaos♦May 25 '12 at 9:56

But your example is problematic, since you did not restrict the cost of calculating $f$. If you make no such restriction, you need entropy exceeding the output size, i.e. a true RNG, and not a PRNG.
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CodesInChaos♦May 25 '12 at 9:57

@CodeInChaos I was just using it as an example. If I were really writing that in a document, I'd put something like "where $f(x)$ runs in polynomial time or better".
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PolynomialMay 25 '12 at 10:10

If you really wanted a symbol for that, I suppose you could borrow a notation from probability theory and write $f \perp k$ for "$f$ is independent of $k$". But that's definitely not standard usage, so you're going to have to define it explicitly.